This invention relates to a drawing compass, and more specifically to a novel compass apparatus and the method of using the same.
Drawing compasses are well known as instruments for marking circles or arcs on draft paper or other surfaces. A traditional compass usually comprises of a handle and two legs with their upper ends pivotally attached to the handle. The free end of the first leg may be a pin or stylus.
The free end of the second leg may be a marking instrument such as a pencil, pen or chalk. The free ends of the legs can be moved open or close so that the distance between the pin and the tip of the marking instrument can be adjusted to a desired radius of a circle or arc. The compass is used by placing the pin of the first leg at the center, placing the marking tip at a start point of the circle or arc to be drawn, and twisting the handle to rotate the second leg around the first one with the marking tip scribing on the drawing surface.
Although traditional compasses have been used for many years, they have intrinsic deficiencies in usage. It requires a delicate control and balance of pressure applied on the two legs to keep one leg anchored at the center and the other rotating and scribing on the drawing surface while twisting and rotating the handle. It is difficult, as the compass is rotated by hand, to maintain the delicate pressure balance. When the pressure on marking tip becomes too light, the scribed line may be indistinct. When the pressure becomes too heavy, the friction may hinder the marking tip from scribing and even cause the pivot pin to lose anchor on the drawing surface. The manipulation requires practice and is a challenge for student, occasional users or persons with limited dexterity.
Beam compasses are also known, in which a pivot pin holder and a marking instrument holder are moveably mounted along a rigid intermediate beam. The manipulation of beam compasses requires both hands, one to hold the pivot pin in the center and the other to rotate the marking instrument around the pivotal pin. This type of compasses is generally designed for certain specific purposes and not for general usage.
There is a need for a novel type of drawing compass with easy usage and manipulation.